1. Field of the Invention
The present invention relates to aerated multiphase systems containing an aqueous continuous fluid phase which may include solutes, thus forming an aqueous syrup and disperse phases like gas/air cells, water ice crystals and solid/semi-solid fat globules or aggregates thereof, whereas the disperse phases are that finely structured that their mean diameters are below phase specific critical maximum values and thereby generate a most preferred by consumers, full rich silky-creamy mouth feel at much lower fat content than usual in conventional related products like premium and super premium ice creams, and processes for their manufacture.
2. Description of the Prior Art
In conventional frozen and aerated water-based ice slurries of the ice cream type, creaminess is mainly generated by a disperse fat phase forming globules with diameters between 0.5 and 2 microns, preferably below 1 micron, and/or fat globule aggregates built due to partial coalescence of the primary fat globules. Such interconnected fat globules/fat globule aggregates can form a three-dimensional network thus stabilizing the air cells in the ice cream structure, most obviously when the ice crystals are melted. Fat globule networking in particular at the air cell interface is supported by more hydrophobic fat globule surfaces. Those are more available if emulsifiers like mono-/diglycerides containing a larger fraction of unsaturated fatty acids support the de-hulling of initially protein covered fat globules in the temperature range where a major portion of the fat fraction crystallizes. In ice creams, milk fat is generally used as the main fat component for which the related relevant crystallizing temperature range is below 5 to 8° C. The well stabilized air cells are mainly responsible for the creaminess and texture sensation during ice cream melting in the mouth. The more stable the air cell/foam structure in the melted state during shear treatment between tongue and palate, the more pronounced the creaminess is perceived. Another but smaller direct contribution to the creaminess is derived from medium sized fat globule aggregates below 30 micron. If the fat globule aggregates become too large (larger than about 30-50 microns) the creamy sensation turns into a buttery, fatty mouth feel.
It has been demonstrated how the diameter reduction of the fat globules by applying higher homogenization pressure in ice cream mix preparation supports the build-up of a fat globule network, improving air cell/foam structure stability and related creaminess.
The scoop ability of frozen, aerated slurries like ice cream is mainly related to the ice crystal structure, in particular the ice crystal size and their inter-connectivity. Scoop ability is a very relevant quality characteristic of ice creams in the low temperature range between −20C and −15 C, right after removing from the freezer. In conventional ice cream manufacture partial freezing is done in continuous or batch freezers (=cooled scraped surface heat exchangers) down to outlet temperatures of about −5° C. Then the ice cream slurry is filled into cups or formed e.g. at the outlet of extrusion dies. Following this the products are hardened in freezing systems with coolant temperatures of around −40° C. until a product core temperature of about −20° C. is reached. Then the products are stored and/or distributed. After the pre-freezing step in the scraped surface heat exchanger (=ice cream freezer) in conventional ice cream recipes, about 40-45% of the freezable water is frozen as water ice crystals. Another fraction of about 25-30% is still liquid. Most of this fraction freezes during further cooling in the hardening system. In this production step, the ice cream is in a state of rest. Consequently the additionally frozen water crystallizes at the surfaces of the existing ice crystals, thus causing their growth from about 20 microns to 50 microns and larger. Some of the initial ice crystals are also interconnected thus forming a three-dimensional ice crystal network. If such a network is formed the ice cream behaves like a solid body and the scoop ability becomes very poor.
It has been shown that the ice crystal growth during cooling/hardening is claimed to be restricted by the use of anti-freeze proteins. This is also expected to have a positive impact on the ice crystal connectivity with respect to improved scoop ability.
It has also been claimed that the use of other specific ingredients like low melting vegetable fat, polyol fatty acid polyesters or specific sugars like sucrose/maltose mixtures are claimed to soften the related ice cream products thus improving scoop ability and creaminess.
Finally reference has been made to specific processing equipment, mostly single or twin screw cooled extruders, in order to modify the ice cream microstructure for improving the texture and stability properties.
It has not yet been recognized that all of the disperse phases in aerated frozen ice cream-like slurries can be reduced or modified in size and/or connectivity on the basis of a mechanical shear treatment principle. Thus the mechanical shear treatment principle can effectively contribute to the adjustment of microstructure related quality characteristics like scoop ability and creaminess.